# How the Modern LEGO Brick Design Works

> The 1958 patent that defined the iconic LEGO brick with hollow tubes inside, allowing bricks to lock together firmly.

- **Patent:** US 3005282
- **Original title:** Toy building brick
- **Owner:** Interlego AG
- **Granted:** 1961
- **Status:** Public domain (expired)
- **Times cited:** 374
- **Field:** consumer_electronics, mechanical

## What it does

This patent describes the structural design of a toy building brick that features hollow cylindrical tubes on its underside. These tubes are positioned to frictionally engage the walls of other bricks when pressed together. This specific arrangement allows for a stable, interlocking connection that remains secure even when the structure is moved or turned upside down. It transformed simple plastic blocks into a versatile construction system.

## What it does NOT cover

- Does not cover bricks without the specific hollow tube configuration on the underside
- Does not cover non-plastic materials or different geometric shapes like spheres or pyramids
- Does not cover the specific chemical composition of the plastic used

## The clever bit

The innovation was placing hollow tubes inside the brick to create a friction-fit with the studs above, rather than relying on simple gravity or loose stacking.

## Real-world examples

1. Standard 2x4 LEGO bricks
2. LEGO Technic beams
3. LEGO Duplo blocks

## Why it matters

This design is the foundation of the entire LEGO brand. By solving the problem of structural instability in early plastic blocks, it enabled the creation of complex, multi-story models that do not fall apart during play.

## Frequently asked questions

### What does How the Modern LEGO Brick Design Works cover?

The 1958 patent that defined the iconic LEGO brick with hollow tubes inside, allowing bricks to lock together firmly.

### Who owns patent US 3005282?

Interlego AG owns this patent, granted in 1961.

### When does this patent expire?

This patent has expired and is now in the public domain — anyone can use the invention freely.

### What is patent US 3005282 cited by?

This patent has been cited by 374 later patents that build on its ideas.

### What problem does this patent solve?

This design is the foundation of the entire LEGO brand. By solving the problem of structural instability in early plastic blocks, it enabled the creation of complex, multi-story models that do not fall apart during play.

### What does this patent NOT cover?

Does not cover bricks without the specific hollow tube configuration on the underside

**Full plain-English explainer:** https://patentbrief.org/patent/us/3005282/lego-toy-brick

**Original patent:** https://patents.google.com/patent/US3005282

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_Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._


## Related patents

Semantically similar inventions in the PatentBrief corpus:

- [How TinkerToy's Original Wooden Construction Blocks Work](https://patentbrief.org/patent/us/1113371/tinkertoy-pajeau) — A 1914 patent for a modular toy system using wooden sticks and circular hubs with holes to build complex three-dimensional structures.
- [How A.C. Gilbert Designed Early Interlocking Toy Construction Blocks](https://patentbrief.org/patent/us/1066809/erector-set-gilbert) — A 1913 patent by A.C. Gilbert for a system of toy building blocks designed to snap together to create structures.
- [The Invention of Lincoln Logs](https://patentbrief.org/patent/us/1351086/lincoln-logs-wright) — A 1920 patent for a toy construction system using notched wooden logs to build miniature cabins and structures.
- [How the Hula Hoop Works](https://patentbrief.org/patent/us/3079728/hula-hoop-wham-o) — A 1963 patent for a lightweight, rigid plastic hoop designed to rotate around a human waist through rhythmic body movements.
- [How the Slinky Toy Works](https://patentbrief.org/patent/us/2415012/slinky-toy) — The original 1947 patent for the Slinky, a helical spring toy designed to walk down stairs through the transfer of energy.